1. Field of the Invention
The present invention is generally related to a clutch mechanism for a marine propulsion system and, more particularly, to a clutch mechanism that allows a shift mechanism to move beyond the degree of rotation required to move a clutch member into torque transmitting relation between a driveshaft and a driven shaft, such as a propeller shaft.
2. Description of the Prior Art
Those skilled in the art of marine transmissions are aware of many types of clutch actuators that can be used to move a clutch member into engagement with either a forward or reverse gear and also move the clutch member into a neutral position. Gear selecting mechanisms used in conjunction with marine propulsion systems typically utilize a shift shaft that causes a clutch actuator to move between the forward, neutral, and reverse gear positions.
U.S. Pat. No. 4,223,773, which issued to Croisant et al. on Sep. 23, 1980, discloses a drive engaging apparatus. A clutch apparatus for a marine drive lower gear case includes a propeller shaft rotatably mounted in a gear case housing. A drive gear for both forward and reverse is positioned in the housing coaxial with the propeller shaft and a clutch member is rotatably fixed on the propeller shaft and movable axially into drive engagement with the drive gear. Clutch engaging elements are provided on opposite portions of the drive gears and the clutch member. Shift means utilizing a positive acting cam means positively move the clutch member into and out of engagement from the drive gears. The shift means also include a releasable latch means to positively maintain the shift means in the engaged position and a preloading means between the shift means and the clutch member to snap the clutch member into engagement.
U.S. Pat. No. 4,986,774, which issued to Wantz on Jan. 22, 1991, discloses a desmodromic shift adaptor for a counter-rotating propeller shaft assembly. An adaptor member for accommodating use of a desmodromic cam-actuated shifting mechanism into a convention propeller shaft cavity formed in the lower end of the gearcase of a marine propulsion system is disclosed. In a system of this type, forward thrust on the propeller shaft is transferred to the gearcase at a point aft of the forward and reverse gears mounted about the propeller shaft. The adaptor member includes a cup, which is adapted to mount the fore one of the forward and reverse gears through a bearing member. The adaptor member further includes an internal passage within which is disposed the movable cam of the shifting mechanism and an opening is in communication with the passage for allowing connection of the shift shaft to the shifting cam after assembly of the adaptor member into the gearcase cavity.
U.S. patent application Ser. No. 10/090,202 (M09567) which was filed by Sawyer et al. on Jan. 3, 2003, discloses a shift mechanism for a marine propulsion system. A gearshift mechanism is provided in which a cam structure comprises a protrusion that is shaped to extend into a channel formed in a cam follower structure. The cam follower structure can be provided with first and second channels that allow the protrusion of the cam to be extended into either channel which accommodates both port and starboard shifting mechanisms. The cam surface formed on the protrusion of the cam moves in contact with a selected cam follower surface formed in the selected one of two alternative channels to cause the cam follower to move axially and to cause a clutch member to engage with either a first or second drive gear.
U.S. patent application Ser. No. 10/211,186 (M09615) which was filed by Sawyer on Aug. 2, 2002, discloses a gear selector actuation system for a marine propulsion device. An actuation system for a gear selector of a marine propulsion device incorporates an adjustable motion directing component that changes the path of travel of an actuator end of a push-pull cable. This adjustable change creates a beneficial effect by changing the relative positions of a shift shaft and associated link arms in relation to positions of a wire within a sheath of a push-pull cable.
In a typical application of a marine propulsion system, a throttle and shift handle is provided near the helm of a boat for the operator of the marine vessel in order to allow the operator to move the handle to change the gear selector between neutral, forward, and reverse gear positions. The manually controllable throttle and shift handle is typically connected to the clutch mechanism of the marine propulsion system by a push-pull cable. A push-pull cable typically comprises a metal wire within an outer tubular sheath. The sheath is generally attached to various locations of the marine vessel and the wire is able to slide axially within the outer sheath to transfer force from the manually controllable throttle and shift lever to the clutch mechanism of the marine propulsion device.
One inherent problem with push-pull cables is that the axial movement of the wire at one end of the cable (e.g. at the manually controllable throttle and shift lever) is not necessarily identical to the magnitude of movement of the wire at the opposite end of the push-pull cable (e.g. at the marine propulsion device). This can be caused by bending of the wire within the surrounding sheath because of necessary radial clearances between these two components. As a result, when moving the manually controllable throttle and shift lever in one direction, the wire at the handle may actually move more than the resulting movement of the wire at the clutch mechanism, at the opposite end of the push-pull cable. In the opposite direction, this same problem may or may not exist. This condition, which is inherent in push-pull cables, is exacerbated by increased length of the push-pull cable.
It would be significantly beneficial if a clutch actuation system could be provided which accommodates the varying differences in movement between the throttle and shift handle, which is manually controlled by the operator of the marine vessel, and the actual clutch actuation mechanism of the marine propulsion system.
The patents described above are hereby expressly incorporated by reference in the description of the present invention.
A clutch mechanism for a marine propulsion system, made in accordance with the preferred embodiment of the present invention, comprises a cam member supported for rotation about a first axis. The cam member has a first cam surface. A cam follower is supported for axial movement parallel to a second axis. The cam follower has a first cam follower surface. The first cam surface and the first cam follower surface are shaped to cause axial movement of the cam follower in response to rotational movement of the cam member between a first rotational position and second rotational position. The first cam surface and the first cam follower surface are also shaped to allow the cam member to rotate between the second rotational position and a third rotational position without causing the cam follower to move parallel to the second axis.
The first cam follower surface is formed as a surface of a cavity formed in the cam follower and comprises a first cam follower surface segment and a second cam follower surface segment. The first cam follower surface segment is shaped to cause the cam follower to move parallel to the second axis in response to rotational movement of the cam member between the first and second rotational positions. The second cam follower surface segment is shaped to allow the cam member to rotate between the second and third rotational positions without causing the cam follower to move parallel to the second axis.
The first cam surface and the first cam follower surface are shaped to remain in continual contact with each other during rotation of the cam member between the first and second rotational positions and between the second and third rotational positions.
The present invention further comprises a shift shaft connected in torque transmitting relation with the cam member. The shift shaft is supported for rotation about the first axis. A control member is rotatably attached to the cam follower for axial movement in coordination with the cam follower parallel to the second axis. A clutch member is attached to the second member for coordinated rotation and axial movement parallel to the second axis with the control member.
The cam member and the cam follower are shaped in a symmetrical manner so that the action of the fist cam surface and the first cam follower surface are replicated, in opposite directions, by a second cam surface and a second cam follower surface because of the symmetry of the components. The second cam follower surface comprises third and fourth cam follower surface segments which operate in a manner similar to the first and second cam follower surface segments, but in opposite directions because of the symmetry of the components.
In a preferred embodiment of the present invention, the first and second axes are generally perpendicular to each other.